In one aspect the present invention relates to an improved method for making stable gel structures which results in increased production rates, lower costs, and reduced weight. In another aspect, the invention relates to a lightweight preformed stable gel composition which comprises a stable gel throughout which glass microspheres have been dispersed. In still a further aspect, the invention relates to structures made from the lightweight gel.
Gels have been heretofore used for a variety of purposes which utilize the characteristic behavior of gels to distribute a force applied thereto radially in all directions. For example, gels have been used in the construction of cushions to distribute weight uniformly and to absorb shock. U.S. Pat. Nos. 3,308,491 issued to Spence on Mar. 14, 1967 and entitled "Cushion Structure" and 3,548,420 issued to Spence on Dec. 22, 1970 and entitled "Cushion Structure" disclose cushions that provide uniform distribution of a patient's weight to prevent pressure necrosis when confined for long periods in a bed or wheelchair or as padding in artificial limbs. Cushions of this type may also be employed as floormats to relieve fatigue for workers who must stand for long periods such as on an assembly line.
Preformed stable gel has also been employed in the manufacture of prosthetic devices to simulate the feel and movement of the human body, and, in particular, as disclosed by U.S. Pat. No. 4,019,209 issued to Spence on Apr. 26, 1977 and entitled "Artificial Breast Form and Method of Forming".
The present invention includes preparing a reaction mixture which will form on reaction a self-contained stable gel in which void spaces have been provided by dispersion of glass microspheres throughout. The reaction mixture containing glass microspheres is poured into a mold of any desired shape. The resulting preformed stable gel structure which is sticky may be covered with a variety of coverings dependent on the function of the structure is intended to perform. Preferably the covering selected does not substantially constrain the gel, for example, a latex rubber or an elastic fabric.
A disadvantage of structures utilizing previous gel compositions is that the resulting structures were relatively heavy. The formed stable gel with glass microspheres dispersed throughout made in accordance with the present invention is lighter in weight and more economical to manufacture than gels formed entirely of gel material. While lighter and more economical to manufacture, the lightweight gel composition of the present invention retains the capability of absorbing relatively large shearing forces without fracturing, remains stable over relatively wide temperature range, is nonfriable and hypoallergenic. The novel features believed characteristic of the invention are set forth in the appended claims.